1. Field of the Invention
The present invention relates to an embroidery sewing machine, and more particularly, to a clutch structure for a presser foot in an embroidery sewing machine, which upon a head-interval adjusting operation, can prevent unnecessary driving of a presser foot (a cloth pressing member), thereby preemptively avoiding the occurrence of vibration and noise caused by the unnecessary driving of the presser foot, as well as unnecessary wear of a needle bar installed in a needle bar support case so as to be able to move up and down, a presser foot support, and a presser foot holder.
2. Description of the Related Art
Generally, an embroidery sewing machine is a biaxial positioning control machine, in which an embroidery stitch frame for fixing fabric undergoes horizontal motion in x-axis and y-axis directions while a needle bar moves up and down.
Since such an embroidery sewing machine does needlework while the embroidery stitch frame, holding the fabric, is moved in x-axis and y-axis directions, the precision of movement of the embroidery frame, and the uniformity of speed thereof, have a close relationship to the quality of an embroidered pattern.
Accordingly, a drive source of the embroidery sewing machine, which transfers the needle bar in vertical directions and the embroidery stitch frame in the x-axis and y-axis directions, is generally implemented with a servo motor, which can be precisely controlled, or a motor, the position of which can be controlled.
FIG. 1 is a side elevation view illustrating the drive structure for a presser foot of a conventional embroidery sewing machine in the mounted position, FIG. 2 is a perspective view illustrating the drive structure for the presser foot shown in FIG. 1, in which a height adjustment mechanism is installed, and FIG. 3 is an enlarged perspective view of part “A” of FIG. 2.
As shown in FIGS. 1 and 2, when an upper shaft 104 rotates, a presser foot drive cam 112, coupled to the upper shaft 104, rotates in cooperation therewith. In response to the rotation of the presser foot drive cam 112, a presser foot drive cam transmission member 110 vertically reciprocates according to the amount of eccentricity of the presser foot drive cam 112.
As the presser foot drive cam transmission member 110 moves vertically, a presser foot drive lever 114, connected to the lower end of the presser foot drive cam transmission member 110, vertically pivots around a certain pivot point. In cooperation with this action, a presser foot drive block 118, connected to the presser foot drive lever 114 via a presser foot drive link 116, vertically reciprocates on a needle bar guide shaft 130.
As the presser foot drive block 118 moves vertically, a presser foot holder 118a, fastened to a presser foot holder gripper (not shown), which is housed inside the presser foot drive block 118, vertically moves in cooperation with the presser foot drive block 118. In cooperation with this action, a presser foot assembly (not shown), fastened to the presser foot holder 118a, also moves vertically. Furthermore, a needle bar 132, connected to the bottom of the presser foot holder 118a, vertically moves inside a sewing head (not shown), and a presser foot 128, coupled to the lower end of a presser foot support 124, also vertically operates.
Meanwhile, in the case where a height adjustment mechanism is installed in the drive structure for the presser foot, the pivot point 114a of the presser foot drive lever 114 can be moved up and down.
That is, as shown in FIGS. 2 and 3, the height adjustment mechanism acts to displace the pivot point 114a of the presser foot drive lever 114 in a predetermined direction, thereby adjusting the upper dead point and the lower dead point of the presser foot 128, and includes a drive motor 140, a drive pulley 142, operably coupled to the drive motor 140, a follower pulley 143, which is connected to and rotates following the drive pulley 142, and an eccentric member 145, which displaces the pivot point 114a of the presser foot drive lever 114 using the driving force of the drive motor 140.
The eccentric member 145 is connected, at a meshing protrusion 145c protruding from the center of one side thereof to realize a predetermined amount of eccentricity, to the pivot point 114a of the presser drive lever 114, so that the pivot point 114a of the presser foot drive lever 114 can be displaced upward or downward by the eccentric member 145 connected to the following pulley 143.
The position of the upper and lower dead points of the presser foot 128 can be easily and correctly controlled, since the pivot point 114a of the presser foot drive lever 114 can be displaced upward or downward through the control of the drive motor 140. Accordingly, this makes it possible to automatically control a sewing operation in response to the thickness of a sheet of cloth to be sewn, and to adjust the height of the presser foot 128 by displacing the pivot point 114 of the presser foot drive lever 114. In a sewing operation, when a sheet of cloth to be sewn is relatively thick, the height adjustment mechanism is operated to raise the height of the lower dead point of the presser foot 128. When the sheet of cloth to be sewn is relatively thin, the height adjustment mechanism is operated to lower the height of the lower dead point of the presser foot 128.
Meanwhile, during the above operation, the presser foot holder 118a is fixed to the presser foot drive block 118, so that both are operated together upon the driving of the needle bar. This action occurs similarly to a non-embroidery sewing head in an head-interval adjusting operation conducted such that when the lateral width of the embroidery is larger than the interval of the sewing head, the action of an odd- or even-numbered needle bar 132 of the sewing head must be stopped, or the driving of the needle bar 132 must be interrupted for a long period and repeatedly, which is problematic. Further, there is a problem in that upon such an operation, as the presser foot 128 is driven in the non-embroidery sewing head, vibrations and noise occur inside the sewing arm 102 due to the unnecessary driving.